It is generally recognized that bisphenols are important starting monomers for the synthesis of a variety of high performance thermoplastic polymers and resins. Bisphenol-A or 4,4'-isopropylidene diphenol of the formula, ##STR1## is generally synthesized from phenol and acetone using an acid catalyst. In addition to bisphenol-A of formula (1), 2,2-(2,4'-dihydroxydiphenol)propane or the "ortho" isomer of the formula ##STR2## is also formed as a comonomer with bisphenol-A when the acetone process is employed, as taught, for example by Schlichting et al, U.S. Pat. No. 3,359,281.
An alternative procedure for making isopropylidene bisphenols which substantially eliminates any possibility of side reactions, as shown by the above described acetone process, is by the acid condensation of phenol with either the corresponding para-hydroxy-.alpha.,.alpha.-methylbenzyl alcohol, as shown by the following equation, ##STR3## or by employing phenol with the corresponding isopropenyl phenol which is shown as follows: ##STR4##
Experience has shown that the corresponding ortho-isomer of formula 2 cannot be made directly using either of the above alternative procedures. A self condensation of the corresponding ortho-hydroxybenzyl alcohol, or ortho-isopropenyl phenol, proceeds at a faster rate than the intercondensation with phenol.